The present invention relates to a door control unit for electronically locking and unlocking one or more doors.
Door control units for electronically controlling the locking and unlocking of a door are well known in the art, as described for example in U.S. Pat. No. 3,889,501, among others.
In general, doors may be unlocked electronically by forming a series of holes, notches or apertures along the shaft of a key in a predetermined arrangement to form encoded clocking and data signals which can be "read" by electronic detection circuitry installed within the door to permit unlocking of the door when the proper encoded signals are detected.
A disadvantage of prior art units is that they are not easily adaptable to presently existing door locks within the door, such as in the door knob, as additional locking structure must be installed in the door to provide the electronic mode of operation, which increases the cost of the system.
The capability of remotely changing the "combination" of the particular door lock is also known, but in order to achieve this, the combination itself has generally been located in a memory location in a master control unit, which requires continuous communication between the door unit and the master unit. Should a power failure occur, the door control unit must be switched to a mechanical mode of operation for unlocking the door, which requires additional locking structure to be included within the door itself, as the electronic mode of operation of the system is then not possible.
In prior art systems such as described in U.S. Pat. No. 3,926,021, those systems provide a reading or decoding device in the door itself for decoding the combination which is in the form of a data card. These systems generally require complex decoding or reading structure to be ihcorporated into the door lock itself.
Another problem occurring with prior art systems is that dirt and dust can collect in the hollow spaces or apertures of the encoded keys, which can affect accurate decoding of the key resulting in failure of the door control unit to unlock the door as desired.
In view of the above background, it is an objective of the present invention to provide a door control unit that is easily adaptable to presently existing doors while additionally containing the combination of the lock within the door control unit itself, thereby providing the capability of remote changing of the combination of the door lock from a master control unit should the need arise, while remaining essentially independent of the master control system, thereby providing an electronic mode of operation even in the event of a power failure.